The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Engines typically include a camshaft to actuate intake and exhaust valves. Some camshafts are concentric camshafts that provide for relative rotation between the intake and exhaust lobes. The intake lobes may be fixed to an outer shaft for rotation with the shaft and the exhaust lobes may be rotatably supported on the shaft. Alternatively, the exhaust lobes may be fixed to the outer shaft for rotation with the shaft and the intake lobes may be rotatably supported on the shaft. In either arrangement, the lobes that are rotatably supported on the shaft may use an outer surface of the outer shaft as a bearing surface. The use of the outer surface of the shaft as a bearing surface may require tighter tolerances for the outer diameter of the outer shaft, and therefore additional machining operations resulting in additional cost.